1. Field of the Invention
The present invention relates to a plasma display panel and, more particularly, to a plasma display panel capable of minimizing luminance deterioration even when employing a colored fluorescent layer and improving a bright room contrast ratio.
2. Description of the Related Art
In general, a plasma display panel is a display device that may use vacuum ultra-violet (VUV) rays emitted from plasma obtained through gas discharge so as to excite a fluorescent material. The excited fluorescent material may generate visible light of red (R), green (G), and blue (B), so that an image may be displayed.
For example, an alternating current (AC) type plasma display panel may have a structure in which address electrodes may be formed on a rear substrate and covered with a dielectric layer. Barriers may be disposed between the address electrodes on the dielectric layer in a stripe pattern. Fluorescent layers of red (R), green (G), and blue (B) may be formed at the barriers. On a front substrate facing a rear substrate, display electrodes, e.g., pairs of sustain electrodes and scan electrodes, may be formed along a direction that crosses the address electrodes. The display electrodes may be covered with a dielectric layer and an MgO protective layer. A discharge cell may be formed at a position where the address electrode on the rear substrate crosses the pair of the display electrodes on the front substrate. Millions or more unit discharge cells may be arrayed in a matrix pattern inside the plasma display panel.
In order to operate the discharge cells of the plasma display panel, memory characteristics may be used. More specifically, in order to generate discharge between the pairs of sustain and scan electrodes which may be included in the display electrode, a potential difference greater than a predetermined voltage may be required. The boundary of the voltage may be called a firing voltage Vf. When a scan voltage and an address voltage Va are applied to the scan electrode and the address electrode, respectively, discharge may occur, and plasma may be formed in the discharge cell. Electrons and ions of the plasma move toward electrodes having opposite polarities from each other.
Each electrode of the plasma display panel may be coated with a dielectric layer, so that most of the moved space charge may be accumulated on the dielectric layer having an opposite polarity. Accordingly, net space charge between the scan and the address electrodes may become lower than an address voltage Va that is applied in advance, so that discharge may be decreased, and address discharge may be terminated. In this case, a relatively small amount of electrons may be accumulated on the sustain electrode, and a relatively large amount of ions may be accumulated on the scan electrode. Charge accumulated on the dielectric layer covering the sustain and scan electrodes may be called a wall charge Qw, and space charge formed between the sustain and scan electrodes by the wall charge Qw may be called a wall voltage Vw.
In a case where a discharge sustain voltage Vs may be applied to the sustain and scan electrodes, when a value Vs+Vw of adding the discharge sustain voltage Vs and the wall voltage Vw is larger than the firing voltage Vf, sustain discharge may occur in the discharge cell. VUV generated at this time may excite a corresponding fluorescent material so as to emit visible light through the transparent front substrate.
However, when an address discharge between the scan and address electrodes does not exist, e.g., when the address voltage Va is not applied, the wall charge may not be accumulated between the sustain and scan electrodes, and as a result, the wall voltage between the sustain and scan electrodes may not exist. In this case, only the discharge sustain voltage Vs applied to the sustain and scan electrodes may be formed in the discharge cell. In addition, since the discharge sustain voltage Vs may be lower than the firing voltage Vf, gas space between the sustain and scan electrodes may not be discharged.
There have been various attempts to improve the bright room contrast ratio by increasing a black area ratio that may be a ratio of a black color in the plasma display panel operated as described above, i.e., a method of using a complementary color relation has been developed.
In the plasma display panel using the complementary color relation, the dielectric layer of the front substrate may be colored with a shade of blue, and the barriers of the rear substrate may be colored with a shade of red in order to improve the bright room contrast ratio.
In addition, in the plasma display panel using the complementary color relation, the fluorescent layers on the rear substrate may be colored with a shade of red similar to the barriers in order to further improve the bright room contrast ratio.
However, although the plasma panel display improves the bright room contrast ratio by coloring the fluorescent layers with the shade of red, a large amount of visible light generated in the discharge cell may be absorbed by the fluorescent layers colored with the shade of red, so that luminance may be decreased.